1. Field of the Invention
The present invention relates to a technique capable of improving the electrical characteristics of a semiconductor device and, in particular, to a nickel-silicon compound forming method, semiconductor device manufacturing method, and semiconductor device which can improve the electrical properties of a transistor.
2. Description of the Related Art
Recently, various types of semiconductor devices represented by an LSI have been greatly developed owing to micronization and high-integration of various types of semiconductor elements represented by a transistor. One factor of this may, for example, be a size reduction in a transistor which leads to a lower resistance and a larger amount of current flow on a small transistor. However, as the on resistance of the transistor decreases, the parasitic resistances in the source, drain, and gate which are the main parts of the transistor become non-negligible. To decrease the parasitic resistances in, e.g., a source, drain, and gate, a compound called a silicide or salicide that is a compound of a metal and silicon has been started in use. For example, titanium (Ti), tungsten (W), or cobalt (Co) is generally used as a material of a silicide.
However, as the gate of a transistor nowadays has a size of 50 nm or less, nickel (Ni) has received attention as a silicide material with lower resistance. For example, nickel mono silicide (NiSi) has a lower contact resistance and resistivity than that of a silicide containing Ti, W, or Co. Thus, NiSi has been expected as a feature silicide or salicide material that is to form the main part of a transistor.
In a general semiconductor device manufacturing process, it is ideal to form an NiSi film capable of withstanding high temperatures of 500° C. or more. However, after an Ni film is formed on an Si film, an NiSi film is typically formed by increasing the temperature to near 350° C. at once. This is because when the NiSi film is to be formed by increasing the temperature to near 500° C. at once, cohesion occurs in the NiSi film, and its composition changes into NiSi2 to increase the resistivity. To avoid this problem, it has been a common practice to form an NiSi film at a low temperature near 350° C. Consequently, annealing at a high temperature cannot be performed after NiSi film formation, and this prevents practical use of the film in the various types of semiconductor devices represented by LSIs.